1. Field of the Invention
The present invention relates to a current generation supply circuit, a display device comprising the current generation supply circuit, and a drive control method of the display device; and more particularly related to a display panel comprising with display pixels comprising current control type light emitting devices for executing a light generation operation at predetermined luminosity gradations based on gradation currents corresponding to the display signals. Furthermore, the present invention is related to a current generation supply circuit which advances miniaturization of the display panel while acquiring superb image quality.
2. Description of the Related Art
In recent years, as the next generation display device (display) following liquid crystal displays (LCD's) which at present are abundantly used as monitors and displays for personal computers and video equipment, Research and Development (R&D) toward full utilization of self-luminescence type display devices (display devices) comprising a display panel arranged in a matrix form consisting of self-luminescent type optical devices such as organic electroluminescent devices (hereinafter, referred to as “organic EL devices”), in organic electro luminescent devices or Light Emitting Diodes (LEDs), etc. is actively being developed.
In such a self-luminescent type display, and particularly a self-luminescent type display which applies an active-matrix drive method and as compared with an LCD provides a more rapid display response speed as well as there is no viewing angle dependency. As backlight is not needed like an LCD, this very predominant feature enhances the clarity of displayed images and makes even higher contrast and higher luminosity more practicable in the years ahead. Thus, the likelihood is inevitable of further miniaturized, low-powered and thin-shaped displays in the future.
This self-luminescence type display according to such an active-matrix drive method, in summary, comprises a display panel with display pixels containing light emitting devices arranged near each of the intersecting points of the scanning lines positioned in rows and the data lines positioned in columns; a data driver which generates gradation signals corresponding to the image display signals (display data) for supplying each of the display pixels via the data lines; and a scanning driver which sequentially applies scanning signals at predetermined timing to sets specified lines of the display pixels as the selection state. By supplying gradation signals from the data driver to each of the display pixels set as the selection state by the scanning driver, each of the display pixels (light emitting devices) execute the light generation operation at predetermined luminosity gradations corresponding to the display data and is configured so that the desired image information is displayed on the display panel.
As the drive methods in such a display, the voltage specification type drive method and the current specification type drive method are primarily known. Notably, the voltage specification type drive method controls the current values of the light generation drive currents flowed to each of the light emitting devices for executing the light generation operation by predetermined luminosity through adjusting the current values (gradation signal voltages) of the gradation signals corresponding to the display data applied by the data driver relative to the display pixels (light emitting devices) of specified lines selected by the scanning driver. Further, the current specification type drive method controls the current values of the light generation drive currents flowed to each of the light emitting devices by means of adjusting the current values (gradation currents) of the gradation signals supplied by the data driver.
The active devices (Thin-Film Transistors, etc.) which constitute these pixel driver circuits are susceptible to characteristic changes influenced by the external environment and deterioration with age. Accordingly, variations in the current values of the light generation drive currents become noticeably greater over a period of time, thereby resulting in the troublesome problem of acquiring the desired luminescent characteristic in a stable state.
Conversely, the current application type drive method has the predominance that the device characteristics can be controlled and suppressed. Configurations of the data driver applicable to the display employing such a current application type method, for example, generate gradation currents corresponding to display data based on reference current supplied via a current supply source line from a current source and are configured so that each of the display pixels can be supplied via each of the data lines. In this instance, as the gradation currents supplied to each of the data lines change corresponding to the display data, the reference current supplied to the current supply source line will also change corresponding to the display data. However, because the capacity component (parasitic capacitance), such as the wiring capacity, etc., exists in the signal wiring for supplying the reference current via the current supply source line is equivalent to charging or discharging at predetermined potential the capacity component which exists in the concerned current supply source line. Therefore, when the reference current supplied particularly via the current supply source line is exceptionally low, the charge and discharge operation takes time and until the potential of the current supply source line is stabilized, a relatively lengthy period is required Here, in order for the charge and discharge operation to the current supply source line to take a certain amount of time as mentioned above and although the time period allocated for generating the drive currents for every data line in the data driver decreases as the number of display pixels increases with miniaturization of the display panel, as the number of data lines and scanning lines increase and the drive time for every scanning line decreases a faster higher speed operation is required. Accordingly, rate control of the operating speed in the data driver originating in the amount of time the charge and discharge operation takes to be completed is highly difficult to contend with in greater miniaturization of the display panel has the disadvantage of causing deterioration of the display quality.